Sensors, and particularly biosensors, are used in many technical fields to analyze a sample and to determine the concentration of an analyte present in the sample and/or to determine other parameters of the sample. Such sensors find use in, for example, water analysis (i.e., drinking water analysis), the food industry, the military and medicine among others.
Biosensors are known that use metal oxides as catalysts, where the catalysts accelerate the conversion reaction of hydrogen peroxide (H2O2), which is mediated by an analyte-specific enzyme. For example, EP Patent Application Publication No. 0 603 154 discloses that biosensor electrode material can include manganese (IV) oxide (MnO2). Additional examples of catalysts disclosed include the following: FeOOH, Fe3O4, Fe2O3, Cr2O3 and V2O5. The biosensors are used with a voltage of between 350 mV to 500 mV. Unfortunately, the risk of these ranges for the working electrode voltage is an undesired reaction of further components (or interferents) in the sample, such as other metabolites or therapeutic agents. Metabolites that can be oxidized in the voltage range of 350 mV to 500 mV are, among others, uric acid and ascorbic acid. A typical example of a therapeutic agent that can be oxidized in this voltage range is acetaminophen. The oxidation of these interferents at the working electrode leads to an undefined increase of the electrode signal. At present, there is not an adequate means to distinguish the signal resulting from the analyte-relevant reaction of the H2O2 and the signal resulting from the undesired reaction of the interferents. Thus, the signal detected by the biosensor can be a mixture of both reactions. As these signals cannot be separated after detection, the analyte signal is overloaded by the interferent signal. Consequently, such measurements may lead to a false and imprecise detection of the analyte.
Catalysts, such as hexacyanoferrate catalysts, also are known that lead to a reduction of the analyte in a negative voltage range, which do not lead to reduced cross-reactions, as oxygen is reduced in the negative voltage range at about −0.1 V to −0.2 V.
Many currently used biosensors therefore show a high cross reactivity with a number of metabolites or other interferents that are present in a living body. As such, there is a need for biosensors applicable in biological systems, such as the living body, to detect analytes, such as glucose or other metabolites, in a precise and reproducible manner.